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Term Paper on Microbes
Term Paper Contents:
- Term Paper on the Meaning of Microbes
- Term Paper on the Types of Microbes
- Term Paper on the Distribution of Microbes
- Term Paper on the Role of Microbes in Various Fields
Term Paper # 1. Meaning of Microbes:
Microbes are single-celled organisms, which make up most of the earth’s biomass. They are the oldest form of life on earth and have evolved for some 3.8 billion years. They have been found in virtually all types of environment, surviving in extremes of heat, cold, radiation, pressure, salt, acidity, and darkness. Normally, in these environments, no other forms of life are found.
Microbes are organisms of microscopic sizes and include bacteria, fungi, algae, protozoa and viruses. Microorganisms have a great impact on many areas of biology and general human welfare. Some are beneficial to man while others are harmful. The beneficial functions include production of bread, cheese, antibiotics, vaccines, vitamins, enzymes and many other products.
Microorganisms occupy an important position in the ecosystem. They are required for the various cycles of nature such as carbon, nitrogen, oxygen and sulphur that take place in the ecosystems. The harmful effects of microbes are that they cause diseases, deteriorate materials like wood, iron pipes and spoil food.
Term Paper # 2. Types of Microbes:
The different types of microbes and their characteristic features have been summarised in Table 1:
i. Bacteria (0.2-100μm):
Prokaryotic, unicellular can be grown in artificial media.
a. Some causes diseases
b. Some perform important role in cycling of elements and contribute to soil fertility.
c. Some play an important role in the food industry.
d. Some spoil food.
ii. Viruses (0.015-0.2μm):
Obligate parasites that cannot be grown in artificial media; require living cells to grow and reproduce.
Causes diseases in humans, plants, animals and other microorganisms.
iii. Fungi such as yeasts (5.0-10.0μm):
Eukaryotic, unicellular and be cultivated in the laboratory.
a. Production of alcohol beverages.
b. Also used as food supplement.
c. Some causes diseases.
iv. Fungi such as moulds (2.0-10.0μm):
Eukaryotic multicellular and be cultivated in the laboratory.
a. Decomposition of many materials.
b. Useful in the production of chemicals such as penicillin.
c. Causes diseases on human, animals and plants.
v. Protozoa (2.0-200μm):
Eukaryotic unicellular organisms.
a. Serve as food for aquatic animals.
b. Some causes diseases.
vi. Algae (1.0μm-many feet):
Eukaryotic unicellular and multicellular.
a. Function as producer in the aquatic environment.
b. Used as food supplement and in Pharmaceutical preparation.
c. Sources of agar to prepare media.
d. Some are toxic.
Term Paper # 3. Distribution of Microbes:
Microbes are found practically everywhere in nature. They are found in the atmosphere, in the deepest oceans and lakes and in the soil. In fact, they are found abundantly in places where there is food, moisture and suitable temperature, a combination of conditions that favours human survival.
Microbes are found on the surface of the body, alimentary tract, mouth, nose, etc. Most of them are harmless to man and human beings possess defense mechanism to resist invasions to those that are potentially harmful.
Term Paper # 4. Role of Microbes in Various Fields:
i. Microbes and Mining:
Microbes have been used in the successful extraction of metals. Useful metals such as copper, iron, uranium, gold, nickel and cobalt are found naturally. For example, copper is found naturally as copper sulphides. It mostly exists as copper pyrites, CuFeS2, which contains copper, iron and sulphur. Copper is extracted from the water that drains through rocks containing the copper ores.
This process is known as leaching and it occurs due to the action of bacteria. The bacteria convert the insoluble metal compounds to soluble metal compounds such as copper sulphate from which copper can be easily extracted. The bacteria responsible for the leaching of metal sulphides are Thiobacillus ferrooxidans and Leptospirillum ferrooxidans. These bacteria are capable of thriving in acid conditions and high temperature. T. ferrooxidans is chemosynthetic, i.e. they obtain the energy by oxidising inorganic substrates.
a. Microbes as Bio-Control Agents:
Bio-control is a term which refers to the use of biological methods to control diseases and pests. Until recently, pests and diseases have been controlled by using pesticides. But these chemicals are toxic and extremely harmful to the environment. They have polluted the useful plants, have killed animals and have polluted the soil. As a remedial measure, biological control is being used extensively now a days as an alternative measure to avoid the problems mentioned above.
Biological Control of Pests and Diseases:
Every organism plays an important role in maintaining the balance in nature. Eradication of an organism is undesirable as the balance will be upset, since the so called ‘pests’ may serve as food to other beneficial predators and insects. Modern agriculture encourages the biological farming approach to reduce the dependence on toxic chemicals and pesticides.
According to this approach the following things have to be considered:
a. The various life forms that inhabit a particular area.
b. The predator and the prey involved, their life cycles, feeding patterns and habitats they prefer.
Some examples of biological control are as follows:
a. The ladybird beetle and dragon flies are useful in getting rid of aphids and mosquitoes respectively.
b. The bacteria, Bacillus thuringiensis (represented as Bt) is used to control butterfly caterpillars. The dried spores of the bacteria are mixed with water and sprayed onto the plants such as brassicas and fruit trees. The larvae found on these plants feed on the bacteria. The larva is killed by the toxins released in the gut.
The other insects are not affected by the bacteria. Recently the gene for the toxin is introduced into the cotton plant by the process of genetic engineering. These plants are resistant to attack by these insect pests and are called Bt-cotton.
c. Plant diseases can be controlled by the free living fungus, Trichoderma.
The baculoviruses are excellent biological control agents of several insects and arthropod pests. An example of this group of virus is Nucleopolyhedrovirus. It is species-specific and attacks only specific organisms. These do not affect plants, mammals, birds, fishes and other insects.
Bioremediation includes processes that use microorganisms or enzymes secreted by them to clear the contamination in the environment such as oil spills and soil contamination. Oil spills that occur in the sea can be cleared by complicated techniques that involve the addition of nitrate and sulphate fertilisers to facilitate the decomposition of the crude oil by oil-eating bacteria. Soil contamination by chlorinated hydrocarbons can also be degraded by bacteria.
b. Microbes as Bio-Fertilisers:
The use of fertilisers to increase food production has had a negative impact on the environment. The recent trend in agriculture is ‘organic farming’, where bio-fertilisers are used. Bio-fertilisers are organisms that increase the quality of the soil and reduce the dependence of chemical fertilisers. These include bacteria, fungi and cyanobacteria.
A classic example of bio-fertiliser is the Rhizobium, which exists in a symbiotic association in the root nodules of leguminous plants. The Rhizobium fixes atmospheric nitrogen and converts it into an usable organic form. Azospirillum and Azotobacter are examples of free living bacteria that can also fix atmospheric nitrogen. The presence of these bacteria increases the nutrient quality of the soil.
Mycorrhiza is symbiotic association of fungus (Glomus) in the roots of higher plants. The fungus absorbs phosphorus from the soil and gives it to the plant. The symbiotic association also has other benefits such as resistance to root borne pathogens, tolerance to salinity and drought and an overall increase in growth and development.
Cyanobacteria are also excellent bio-fertilisers found in both aquatic and terrestrial environments. Anabaena, Nostoc, Oscillatoria are examples of Cyanobacteria. They fix atmospheric nitrogen, add organic matter to the soil and increase the fertility.
ii. Microbes and Alcoholic Beverages:
Yeast is used in Alcohol Industry:
Alcohol is the most common solvent used in the laboratory and chemical industry. It is produced during anaerobic respiration of yeast, i.e. Saccharomyces cerevisiae, which converts sugar to ethanol and carbon dioxide. This is known as alcohol fermentation.
Glucose → Alcohol + CO2 + Energy
Depending on the type of sugar, different types of alcohol can be made.
a. Beer is prepared from the fermentation of maltose by yeast.
b. Wine is made from the fermentation of grape sugar by yeast.
Beer is brewed from barley grain, which is partially germinated to convert the starch to maltose. This process of conversion is known as malting. Gibberellins and amylase are used to speed up the process of germination and to increase the amount of sugar to produce more alcohol. The sugar is extracted by crushing the grain and adding hot water. The liquid obtained after this procedure is known as wort.
Alcohol has two main uses:
a. It is consumed as a social drink by individuals.
b. It is also used as a fuel.